The invention relates to a bearing seal between the inner space of a centrifuge and its drive part, comprising annular sealing elements which elastically surround a drive shaft protective bushing. On the drive side, the sealing elements are exposed to a protective gas, such as nitrogen, which passes through the seal in the inside of the centrifuge.
Centrifuges are particularly used for the separation of suspensions into solids and liquid filtrates. In the pharmaceutical industry and in the production of food items, it is essential to maintain the internal space of the centrifuge which contains the centrifuge drum, clean with respect to the drive part of the centrifuge. A seal between the inner space of the centrifuge and the drive part is also necessary because explosive or aggressive gases which must be kept away from the drive part may be evolved in the course of centrifugation.
It is known to equip the bearing seal with an annular sealing element which is elastically pressed against the drive shaft of the centrifuge or a protective bushing provided on the drive shaft. On the drive side, an inert protective gas streams against the sealing element and passes through a predetermined leak between the sealing element and the drive shaft. This functions to keep the seal free of dirt particles and to ensure that no gases may pass the seal in the opposite direction. Nitrogen is a suitable protective gas in most cases.
It is an object of the present invention to provide a bearing seal between the internal space of a centrifuge and its drive part, which operates reliably, requires little maintenance, and whose parts subject to wear may be easily replaced.
This object is attained by the bearing seal according to the invention, wherein at least two identical sealing elements are arranged in axial succession; the diameter of the protective bushing of the drive shaft is reduced in the contact area of the sealing element closest to the internal space of the centrifuge; and the protective gas passes through the sealing element.
Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments which follows, when considered together with the attached figures of drawings.